個人計算機領域流行用智能電池，這是因為智能電池能提供本個工業標準、高精度氣壓計（gasgauge）系統。智能電池符合智能電池供電系統（SBS）所定義的元件所有工作性能指標，電池具有跟蹤有關電池充電和使用信息的嵌入控制器。通過串行、2線SMBus接口提供信息到系統。可詢問電池信息包括剩余容量、總容量、在現有放電速率下時間余、放電電流、終端電壓等。由于大多數智能電池在總線中可成為主機，所以電池可控制智能電池充電器使其最佳充電。Linear公司LTC1759智能電池充電器IC設計用于控制這類智能電池。另外(wai)，由電(dian)池(chi)提供的(de)安(an)全信號指(zhi)示(shi)電(dian)池(chi)是(shi)(shi)否(fou)呈現在系(xi)統中和(he)是(shi)(shi)否(fou)有熱(re)引(yin)起的(de)告警(jing)或在其他系(xi)統失效(xiao)時(shi)是(shi)(shi)否(fou)電(dian)池(chi)失效(xiao)。SBS顯著特點是(shi)(shi)安(an)全、使用容易和(he)兼容性。

　　SBS規范允許兩種類型智能電池充電器（SBC）：Level2充電和Level3充電器。Level2充電器（如LTC1759）是SMBus上的從機，響應來自電池的命令控制充電。Level3充電器可以是SMBus上的主機或從機，它可詢問電池確定充電信息。SBC與電池化學類型無關。它響應來自電池的命令提供充電電流和充電電壓。電池的零電流（或零電壓）或終止充電報警形式發出充電終止。假若安全信號指標電池不存在或安全充電電池太熱，則充(chong)電也將(jiang)終止。

　　SMBus 為系統(tong)和(he)(he)電(dian)源管(guan)理(li)這樣(yang)的(de)(de)(de)任務提供(gong)了(le)一條控(kong)制(zhi)(zhi)總線，使用(yong)(yong) SMBus 的(de)(de)(de)系統(tong)，設備(bei)(bei)之(zhi)間發(fa)送和(he)(he)接(jie)收消息都是通過 SMBus，而不是使用(yong)(yong)單獨(du)的(de)(de)(de)控(kong)制(zhi)(zhi)線，這樣(yang)可(ke)以節省(sheng)設備(bei)(bei)的(de)(de)(de)管(guan)腳數。 　　使用(yong)(yong) SMBus，設備(bei)(bei)還可(ke)以提供(gong)它的(de)(de)(de)生(sheng)產信(xin)息，告訴(su)系統(tong)它的(de)(de)(de)型號，部件(jian)號等(deng)(deng)，針對(dui)掛起事(shi)件(jian)保存(cun)它的(de)(de)(de)狀態(tai)，報告不同類別(bie)的(de)(de)(de)錯(cuo)誤，接(jie)收控(kong)制(zhi)(zhi)參(can)數，并返回它的(de)(de)(de)狀態(tai)等(deng)(deng)。 　　SMBus器(qi)件(jian)存(cun)在現有7層OSI網絡模型中(zhong)的(de)(de)(de)前3層，即(ji)物理(li)層，數據(ju)鏈路層和(he)(he)網絡層。 　　SMBus最(zui)初的(de)(de)(de)目的(de)(de)(de)是為智能(neng)電(dian)池，充(chong)電(dian)電(dian)池和(he)(he)與其他系統(tong)通信(xin)的(de)(de)(de)微控(kong)制(zhi)(zhi)器(qi)之(zhi)間的(de)(de)(de)通信(xin)鏈路而定義的(de)(de)(de)。SMBus也被用(yong)(yong)來(lai)連接(jie)各種設備(bei)(bei)，包括(kuo)電(dian)源相關設備(bei)(bei)，系統(tong)傳感器(qi)，EEPROM通訊設備(bei)(bei)等(deng)(deng)等(deng)(deng)。

　　LTC1759是一款完整的Level2智能電池充電器。它能在SMBus接口上用接收和譯碼命令自動充電智能電池。LT1759遵從智能電池充電器規范的全(quan)部安全(quan)要求，包括3分鐘定時器（保(bao)護SMBus通信(xin)換效和(he)喚(huan)醒模式期(qi)間鋰離(li)子(zi)電池過(guo)充電）。硬件可編(bian)程電注(zhu)和(he)電壓限(xian)制提供另外(wai)等級保(bao)護，這種保(bao)護由(you)失效軟(ruan)件不可能改(gai)變。

　　LTC1759管理智能電池充電系統的所有復雜事物。它具有SBC依從性、安全、輸出電壓精確、SMBus加速泵、墻式適配器電流限制等特性。它把智能充電器的恒流（CC）、恒壓（CV）、電流模式開關電池充電器電路融合于一身。

　　電路描述

　　LTC1759包括：一個同步、電流模式、PWM降壓開關控制器，一個充電器控制器(qi)，兩個(ge)(ge)控制充(chong)電(dian)(dian)器(qi)參量的10位DAC，一個(ge)(ge)熱敏(min)電(dian)(dian)阻安全(quan)信號(hao)譯(yi)碼(ma)器(qi)，硬(ying)件電(dian)(dian)壓和電(dian)(dian)流(liu)限(xian)制譯(yi)碼(ma)器(qi)和一個(ge)(ge)SMBus控制器(qi)單元（見(jian)圖1）。

 智能電(dian)(dian)(dian)池(chi)或(huo)系統控制(zhi)器通(tong)過SMBus接口命(ming)令對恒(heng)漢和恒(heng)壓(ya)限值(zhi)進行編(bian)程。降壓(ya)變壓(ya)器用N-溝(gou)MOSFET做為(wei)開關，使成本降低(di)、高效率工作。熱敏電(dian)(dian)(dian)阻安(an)全檢測電(dian)(dian)(dian)路檢測電(dian)(dian)(dian)池(chi)存在或(huo)確(que)定電(dian)(dian)(dian)池(chi)溫度是否(fou)允許安(an)全充電(dian)(dian)(dian)。

當通過SMBus傳輸接收恒(heng)流(liu)(liu)值時，它(ta)被RILIMIT定(ding)標和(he)限制到低于編程(cheng)值。此修正(zheng)值編程(cheng)電(dian)(dian)流(liu)(liu)DAC，設置DC充電(dian)(dian)電(dian)(dian)流(liu)(liu)。電(dian)(dian)流(liu)(liu)DAC是10位△∑DAC，當希望充電(dian)(dian)電(dian)(dian)流(liu)(liu)時，它(ta)從PROG引(yin)腳(jiao)吸收電(dian)(dian)流(liu)(liu)（見(jian)圖2）。放(fang)大(da)器PROG引(yin)腳(jiao)吸收電(dian)(dian)流(liu)(liu)（見(jian)圖2）。放(fang)大(da)器CAI感測RSENSE上的(de)(de)壓降并使此電(dian)(dian)壓跨接到RS2（200Ω）；流(liu)(liu)經(jing)RS2的(de)(de)電(dian)(dian)流(liu)(liu)通過電(dian)(dian)流(liu)(liu)鏡(jing)像(xiang)做為(wei)PROG引(yin)腳(jiao)上的(de)(de)上接電(dian)(dian)流(liu)(liu)。流(liu)(liu)經(jing)RS2電(dian)(dian)流(liu)(liu)與來自(zi)PROG引(yin)腳(jiao)電(dian)(dian)流(liu)(liu)相匹配(pei)由CA2實(shi)現恒(heng)流(liu)(liu)工作。由于DAC輸出是一串脈沖，所以(yi)需要平滑電(dian)(dian)容(rong)器對(dui)脈沖濾波(bo)使其變為(wei)DC。

  LTC1759需要兩個電(dian)(dian)源(yuan)。PWM電(dian)(dian)路(lu)在墻式適配器(qi)電(dian)(dian)源(yuan)斷(duan)(duan)開時(shi)(shi)直(zhi)接通過Vcc引(yin)腳運行，邏(luo)輯功(gong)(gong)能(neng)(neng)運行與VDD電(dian)(dian)源(yuan)無(wu)關。PWM電(dian)(dian)路(lu)在去掉AC電(dian)(dian)源(yuan)時(shi)(shi)能(neng)(neng)進入40μA微功(gong)(gong)率停(ting)機(ji)模式，使邏(luo)輯和(he)SMBus工(gong)作能(neng)(neng)保持運行，這(zhe)是Intel ACPI標準所需要的。這(zhe)種分(fen)離電(dian)(dian)源(yuan)也使邏(luo)輯和(he)SMBus能(neng)(neng)根(gen)據系(xi)統設(she)計為員(yuan)的需要運行在3V和(he)5V.為使LTC1759邏(luo)輯功(gong)(gong)耗最小，邏(luo)輯電(dian)(dian)流(liu)由時(shi)(shi)鐘電(dian)(dian)路(lu)激勵，時(shi)(shi)鐘電(dian)(dian)路(lu)當無(wu)動(dong)作時(shi)(shi)停(ting)機(ji)并蘇醒服(fu)務(wu)于SMBus動(dong)作或產生(sheng)中斷(duan)(duan)。一(yi)旦請求服(fu)務(wu)，LTC1759便返回到(dao)休(xiu)眠。

　　當去掉AC電源(yuan)或去掉電池時，通過CHGEN-SDB引(yin)腳(jiao)(jiao)組合發生PWM停機(ji)。LTC1759通過DCDIV通腳(jiao)(jiao)檢測AC損耗(hao)。閾值通常設置恰好低于墻式適配的最(zui)小(xiao)有(you)效電壓。AC電源(yuan)狀(zhuang)態通過SMBus可由(you)系統讀出(chu)。UV引(yin)腳(jiao)(jiao)只用于置PWM電路(lu)進(jin)入微功(gong)率停機(ji)狀(zhuang)態，它直接(jie)連到墻式適配器電源(yuan)。

　　在設計中電(dian)感器(qi)選擇不(bu)是關鍵(jian)，這是因為充電(dian)器(qi)的環路(lu)響(xiang)應在意(yi)地設置很慢。實際的低(di)限值(zhi)為15μH左右，低(di)值(zhi)電(dian)感器(qi)將產生較高的紋波電(dian)流，在輸出需要較低(di)ESR電(dian)容器(qi)。

　　輸出電(dian)(dian)(dian)(dian)容(rong)(rong)(rong)的選擇對(dui)ESR（等效串(chuan)(chuan)聯電(dian)(dian)(dian)(dian)阻(zu)）不(bu)是(shi)很(hen)苛刻，但必須處理來自充(chong)(chong)電(dian)(dian)(dian)(dian)器(qi)(qi)(qi)(qi)(qi)(qi)的所有(you)(you)(you)(you)紋波電(dian)(dian)(dian)(dian)流(liu)(liu)。不(bu)用(yong)(yong)(yong)考慮電(dian)(dian)(dian)(dian)池(chi)的紋波電(dian)(dian)(dian)(dian)流(liu)(liu)，因為(wei)充(chong)(chong)電(dian)(dian)(dian)(dian)器(qi)(qi)(qi)(qi)(qi)(qi)有(you)(you)(you)(you)效阻(zu)抗遠遠大于電(dian)(dian)(dian)(dian)感(gan)器(qi)(qi)(qi)(qi)(qi)(qi)的ESR。很(hen)多電(dian)(dian)(dian)(dian)池(chi)組具有(you)(you)(you)(you)內部(bu)串(chuan)(chuan)聯保護(hu)MOSFET，這提高(gao)了(le)電(dian)(dian)(dian)(dian)池(chi)ESR。在多電(dian)(dian)(dian)(dian)池(chi)配(pei)置中也(ye)有(you)(you)(you)(you)與電(dian)(dian)(dian)(dian)池(chi)串(chuan)(chuan)聯的功(gong)率路由MOSFET，進一步(bu)增(zeng)加(jia)(jia)了(le)電(dian)(dian)(dian)(dian)池(chi)ESR。從充(chong)(chong)電(dian)(dian)(dian)(dian)器(qi)(qi)(qi)(qi)(qi)(qi)觀點，輸入(ru)電(dian)(dian)(dian)(dian)容(rong)(rong)(rong)器(qi)(qi)(qi)(qi)(qi)(qi)ESR可高(gao)達1Ω，使電(dian)(dian)(dian)(dian)容(rong)(rong)(rong)器(qi)(qi)(qi)(qi)(qi)(qi)選擇范圍寬。當采(cai)(cai)用(yong)(yong)(yong)電(dian)(dian)(dian)(dian)阻(zu)或(huo)電(dian)(dian)(dian)(dian)子負載時，可能會發生某種(zhong)不(bu)穩定(ding)(ding)性。增(zeng)加(jia)(jia)300Ω電(dian)(dian)(dian)(dian)阻(zu)器(qi)(qi)(qi)(qi)(qi)(qi)與PROG引腳電(dian)(dian)(dian)(dian)容(rong)(rong)(rong)器(qi)(qi)(qi)(qi)(qi)(qi)串(chuan)(chuan)聯或(huo)在輸出置10μF電(dian)(dian)(dian)(dian)容(rong)(rong)(rong)器(qi)(qi)(qi)(qi)(qi)(qi)能改(gai)善(shan)穩定(ding)(ding)性。在輸出不(bu)需要用(yong)(yong)(yong)陶(tao)瓷電(dian)(dian)(dian)(dian)容(rong)(rong)(rong)器(qi)(qi)(qi)(qi)(qi)(qi)，因為(wei)在很(hen)輕負載電(dian)(dian)(dian)(dian)流(liu)(liu)聲(sheng)頻(pin)下(xia)開關變換器(qi)(qi)(qi)(qi)(qi)(qi)變得不(bu)連接(jie)和(he)在下(xia)降(jiang)周期(qi)開始(shi)時電(dian)(dian)(dian)(dian)容(rong)(rong)(rong)器(qi)(qi)(qi)(qi)(qi)(qi)會造成噪聲(sheng)，應該采(cai)(cai)用(yong)(yong)(yong)鉭(tan)電(dian)(dian)(dian)(dian)容(rong)(rong)(rong)。輸入(ru)電(dian)(dian)(dian)(dian)容(rong)(rong)(rong)選擇由充(chong)(chong)電(dian)(dian)(dian)(dian)器(qi)(qi)(qi)(qi)(qi)(qi)輸入(ru)紋波電(dian)(dian)(dian)(dian)流(liu)(liu)（一般為(wei)最大輸出電(dian)(dian)(dian)(dian)流(liu)(liu)的1/2）決(jue)定(ding)(ding)。對(dui)于4A充(chong)(chong)電(dian)(dian)(dian)(dian)器(qi)(qi)(qi)(qi)(qi)(qi)建議用(yong)(yong)(yong)22μF（50V）陶(tao)瓷電(dian)(dian)(dian)(dian)容(rong)(rong)(rong)器(qi)(qi)(qi)(qi)(qi)(qi)，它一般可處理2A紋波電(dian)(dian)(dian)(dian)流(liu)(liu)。

　　從電(dian)池到(dao)(dao)墻(qiang)式(shi)適(shi)配器(qi)的電(dian)流(liu)保護(hu)由(you)P-溝MOSFET（Q1）提供(gong)。電(dian)壓(ya)比較器(qi)監控跨接在MOSFET上(shang)的電(dian)壓(ya)而(er)且當墻(qiang)式(shi)適(shi)配降到(dao)(dao)電(dian)池電(dian)壓(ya)之上(shang)小于200mV時關閉MOSFET。盡管(guan)價廉的二(er)極管(guan)可用于替代以MOSFET，但MOSFET只增(zeng)加(jia)100mV到(dao)(dao)0.4V低壓(ya)差工作模(mo)式(shi)而(er)不產生額(e)外的熱量。在沒有電(dian)池起動時間，采(cai)用MOSFET附加(jia)二(er)極管(guan)使墻(qiang)式(shi)適(shi)配器(qi)電(dian)源能達(da)到(dao)(dao)Vcc引腳并為PWM控制電(dian)路供(gong)電(dian)。

　　主要(yao)的(de)補償是d PROG引腳上進行；然(ran)而DAC脈沖濾波(bo)要(yao)求確定電容器有(you)效值。脈沖紋波(bo)電流(liu)必(bi)須小平200mV或環路起伏（在輕載充(chong)電電流(liu)時出現(xian)的(de)環路不穩定性）。Vc引腳電容器的(de)主要(yao)功能(neng)是提供自(zi)啟動(dong)支持。必(bi)須有(you)一個1.5K電阻器與Vc引腳電容器串聯以能(neng)恰當(dang)停機(ji)。

　　從熱觀點(dian)考慮，輸出(chu)電(dian)壓在電(dian)池溫度充(chong)(chong)電(dian)范圍內保持大約(yue)0.5%精(jing)(jing)度。精(jing)(jing)度越高，電(dian)流充(chong)(chong)電(dian)容量就越大，而(er)更重要是在電(dian)池中與電(dian)壓基充(chong)(chong)電(dian)終(zhong)端電(dian)路有(you)關的問(wen)題(ti)就會更少。

　　關于(yu)SMBus加速泵，AC適配電流限制(zhi)，安全信號感測，安全電壓(ya)和電流范圍設(she)計等問題在此就不一一詳述。

　　LTC1579遵從智能電池系統組織發表的智能電池充電器標準。充電器控制器也遵從Intel的ACP標準，甚至當沒有AC墻式適配器電源時也能響應系統指令。該充電器提供最寬的電流和電壓工作范圍。LTC1759具有價廉、高性能和安全的特點，比其他智能電池充電器優越。